The Reefkeeping article that Erik linked is one of the better ones out there on HLLE. Notice that carbon is only one of many other conditions known to be associated with this syndrome. To presume that running carbon causes HLLE is a pretty wild and oversimplified assumption. If you are interested in learning more about HLLE, the series of three articles that Steven Pro credits as sources for this article (by Terry Bartelme) were really great reading if you can find them!